This disclosure relates to reducing or eliminating thermal wakes proximate to an optical element of a telescope and/or other optical instrument in which the optical element is positioned by way of thermal control of one or more components supporting the optical element, or by actuation and sensing devices that generate heat during operation.
Conventionally, focusing a telescope via thermal control of one or more support struts or other components supporting an optical element can introduce free-convection thermal wakes (i.e., plumes of differentially heated air) within the optical path of the telescope. These thermal wakes can cause distortion of the optical wavefront and degradation of any resulting imaging or other intended use products. Existing approaches to mitigate such thermal wakes include limiting the total focus travel, and therefore the heat introduced. Further existing approaches include aggressive stirring of the optical cavity air of the telescope to break up the otherwise well-defined thermal wakes. These existing approaches are not suitable for certain applications, such as during optical alignment and in-flight deployments, where in-test difficulties and differences in performance between telescope build, test, sell-off and use may result.